1. Field
Embodiments relate to a sound source recording apparatus and method adaptable to an operating environment, which can record a target sound source at a predetermined level without being affected by characteristics of the sound source or ambient noise.
2. Description of the Related Art
Due to development of digital technologies, many portable devices such as digital cameras and camcorders can record sound when capturing moving images. An intelligent robot, such as a home service robot, which supports household affairs, such as cleaning and errands, while residing together with humans in a residence, also conducts tasks given based on voice recognition due to development of home network technologies.
A device equipped with a sound source recording function receives a signal from a sound source through a microphone. The intensity of the received sound source signal varies depending on distance from the sound source (which will also be referred to as “sound source distance”). If the sound source approaches while the gain of the microphone is constant, a clipping phenomenon in which part of the sound of the sound source is removed occurs when the sound source signal is sampled, reducing the rate of sound source recognition.
In one method that may be employed to solve this problem, the gain of the microphone is compensated according to the sound source distance by performing gain control such that, after an optimal gain for each sound source distance is stored, the gain of the microphone is reduced to decrease the level of the sound source signal that is actually recorded if the intensity of the sound source signal received through the microphone is greater than a predetermined level and is raised to increase the level of the sound source signal that is actually recorded if the intensity of the received sound source signal is less than the predetermined level.
In most cases where such a device operates indoors or outdoors, a microphone mounted on the body of the device receives various sound source signals together with the voice of a speaker as a target sound source.
The method to control the gain of the microphone based only on the intensity of the sound source signal received through the microphone is not very effective in an operating environment in which not only noise generated from household appliances, such as TVs, air conditioners, washing machines, and telephones, that are commonly used at home but also various other noise, such as doorbells, outdoor noise, and conversation between family members are present. This is because the gain of the microphone is automatically adjusted due to changes in the level of ambient noise, which temporarily rises or drops in level, such that the level of recorded voice of the speaker may vary even when the speaker speaks at a constant distance from the device.
In addition, the method to control the gain of the microphone simply based on the sound source distance cannot achieve satisfactory results since the characteristics of each sound source may differ even at the same sound source distance, for example, since the volume of voice spoken by each speaker differs depending on the speaker.